Digital mobile multimedia broadcasting technologies and standards have been developing rapidly in recent years, such as European Digital Video Broadcast Handheld (DVB-H) system, American Media Forward Link Only (MediaFLO) system, mobile cellular based Broadcast and Multicast Services (BCMCS) system and China Mobile Multimedia Broadcasting (CMMB) system, etc. The digital mobile multimedia broadcasting network provides many service contents, such as advertisement, weather forecast, news, sports shows, variety shows, multimedia radio play, movies, etc., to is terminal users thereof; the users can select the service program provided by the mobile multimedia broadcasting by preference.
The so-called mobile TV service, in short, is a service of watching TV programs by using a mobile phone terminal of mobile communication. As an emerging service, compared with the traditional TV being watched by the whole family in the living room, the mobile TV is featured with portability, mobility and privacy. With the popularization of mobile data service and the development of mobile phone video functions, the mobile TV starts to come into people's life gradually. With the continuous improvement in living standard, consumer demands are diversified and fashion-orientated, and it becomes a fashion to watch TV programs on the mobile phone, and it will become a manner for people to enjoy life.
In terms of the development of broadcasting TV services, the traditional radio and TV broadcasting technology has been in the development from an analogue technology to a digital technology, and the device for receiving TV signal also develops from an ordinary desktop TV set to diversified terminals, such as mobile TV, vehicle-bone TV, and handheld TV, etc. In terms of development trend of mobile communication, with the substantial increase in data transmission capacity of mobile communication networks and the continuous improvement of terminal manufacture technologies, it becomes possible to watch TV programs via the mobile phone terminal. Technical progresses in these two aspects open a path for receiving video program content of high quality via the mobile phone terminal and melt the rigid boundary between the two industries, thus prompting an entirely new service mode, i.e. the mobile TV.
Emergency broadcasting is a way for announcing emergency events to the public via a broadcasting communication system. When emergency events occur, such as natural disaster, accident disaster, public health and social security, etc., which result in, or may result in heavy casualties, property loss, ecologic and environmental damage, and serious social danger and public security danger, the emergency broadcasting provides a fast and easy announcing manner. With the emphasis of the nation on various emergency events and the proposing of various public emergency pre-arranged planning, it is very necessary to provide an emergency broadcasting service as a broadcasting technique having a large number of online users. The mobile phone terminal having the function of receiving emergency broadcasting messages can receive the emergency broadcasting messages sent from an emergency broadcasting system.
As shown in FIG. 1, it illustrated is a structural diagram of broadcasting channel frames of the CMMB system. The broadcasting channel frame consists of multiple multiplex frames, and each multiplex frame is composed of a multiplex frame head, a multiplex frame payload and a filling part, while the multiplex frame payload is composed of multiple multiplex subframes.
For example, if 1 second is determined to be the multiplex period and divided into 40 equal portions of time periods (time slots), the multiplex unit is 25 ms. Logically, the multiplex frame and time slot mapping are determined by the configuration of system.
One multiplex frame corresponds to one control or service logical channel, and each multiplex frame is assigned with one multiplex frame identification MF_ID in a range from 0 to 39, with 39 being the maximum value. Wherein the multiplex frame with MF_ID=0 is mapped into the control logical channel for transmitting system control information; the multiplex frame with ML_ID#0 (namely MF_ID=1˜39) is mapped into the service logical channel for transmitting service data.
As shown in FIG. 2, the multiplex frame with the multiplex frame identification being 0 (MF_ID=0) is used for carrying the control information, and the multiplex frame payload in the multiplex frame comprises multiple control information tables, i.e., each multiplex subframe consists of one control information table. The emergency broadcasting message table is carried by the control information table with the table ID number being 0x10.
In the existing CMMB specification, the emergency broadcasting service is put in the multiplex frame carrying the control information (i.e. multiplex frame 0, MF_ID=0) for transmission. The receiver is arranged into multiple reception channels according to the performance of the terminal for receiving the broadcasting message; due to the is limitation of the existing technology, the receiver can be arranged into only two reception channels, i.e. logic channel 0 and logic channel 1. Generally, logic channel 0 is used for receiving the control information multiplex frame (i.e. multiplex frame 0), while logic channel 1 is used for receiving service data multiplex frame (i.e. the non-zero multiplex frame, MF_ID≠0).
In the existing technology, the method for receiving emergency broadcasting messages by the user terminal is that:
the terminal detects the ‘emergency broadcasting indication’ field value in the multiplex frame head. As shown in FIG. 3, 0 represents that there is no emergency broadcasting message; when the field value turns from 0 to non-zero, it shows that there is an emergency broadcasting message in the control information multiplex frame (identified by the message ID); the terminal enters logic channel 0 to receive the control information multiplex frame, and to parse the emergency broadcasting information table consisting of emergency broadcasting table head and emergency broadcasting data segment, etc., (the control information table with the table ID number being 0x10), based on the frame structure as shown in FIG. 2.
When the ‘emergency broadcasting indication’ field in FIG. 3 has a new emergency broadcasting message queue to be sent at the transmitting end, the value of this field progressively increases by 1 circularly in the range of 1-3 (i.e. 01-11); or after all the emergency broadcasting message queues have been transmitted in the broadcasting network, the field value turns to 0. That is to say, the field value changes only under these two circumstances, while the field value does not change in the course of circularly transmitting a same emergency broadcasting message in the broadcasting network.
The ‘concurrent message quantity’ in the emergency broadcasting table head in FIG. 2 is 4-bit field with the value thereof ranging from 0 to 15 for representing the quantity of messages to be sent currently in the emergency broadcasting front end transmitting queue. The receiving terminal can determine whether to receive all the emergency broadcasting messages in this message queue according to the field. The message ID is used for identifying the emergency broadcasting message being sent currently in the control information multiplex frame.
The existing technology for receiving emergency broadcasting messages by the terminal has the following disadvantages:
(1) the terminal does not enter the mobile TV, until the emergency broadcasting transmitting front end continuously transmit multiple emergency broadcasting messages simultaneously, and the terminal can not receive all the emergency broadcasting messages until the end of the transmitting period of the multiple emergency broadcasting messages;
(2) if logic channel 1 has been occupied to receive the TV service information at the moment when the user enters the mobile TV and is watching TV, and the emergency broadcasting transmitting front end continuously transmits multiple emergency broadcasting messages simultaneously, if the terminal always uses logic channel 0 to receive the control information multiplex frame, it consumes a large amount of power and wastes a large number of resources in the course of reception, though it can receive all the emergency broadcasting messages.